Ski trimming lock



, p w. ARMSTRONG 2,256,542

SKI TRIMMING LOCK Filed Feb. 15, 1940 2 Sheets-Sheet l I A TTOR/Vf/S Sept. 23, 1941. w. ARMSTRONG SKI TRIMMING LOCK Filed Feb. 15, 1940 2 Sheets-Sheet 2 Patented Sept. 23, 1941 SKI TRIMIVHNG LOCK William Armstrong, New York, N. Y., assignor to The Dowty Corporation, Wilmington, DeL, a

corporation of Delaware Application February 15, 1940, Serial No. 319,074.

9 Claims.

This invention relates to a ski trimming lock which is adapted to lock the ski against rotation when the airplane to. which the ski is attachedis in the air and to automatically unlock the ski so as to allow free pivotal movement thereof within limits when the airplane is on theground.

It is an object of the present invention to provide a ski lock of the foregoing typ which is. simple in construction and in operation, which is light in weight, which offers low resistance to the air and-which is adapted to operate over long periods of time with a minimum of maintenance.

Another object is to provide a ski lock wherein reliance is placed upon stops which are disposed on the ski and on a part of the landing gear which moves relative to the ski during landing, take-E or taxiing. The arrangement is preferably such that these stops are moved apart from one another when the ski is moved towards the airplane and are moved into engagement with one another upon take-off when the ski moves away from the airplane.

Still other objects will more fully hereinafter appear.

In the. accompanying drawings;

Fig. 1 is a side fragmentary elevation of an airplane equipped with a ski. type landing. gear embodying one form of ski lock of the present invention.

Fig. 2 is an enlarged side elevation, partly in section, of the ski mounting and lock.

Fig. 3 is a rear view of Fig. 2.

Fig. 4 is a side elevation of the device with the airplane on the ground with its. tail up.

Fig. 5 is a perspective exploded View of the locking device.

Fig. 6 is a side elevation of the locking device with the airplane on the ground with the tail down.

Fig. 7 is a similar view with the airplane on the ground with the tail down and with the ski deflected in such manner as to elevate its front.

portion.

Figs. 8 and 9 portray a modification. In these;

Fig. 8 is a side elevation showing the ski looked as in flight.

Fig. Qis a similar view showing the device with the airplane on the ground with the tail down.

Referring to the drawings in detail, I designates the airplane body which is provided with a downwardly extending landing strut 2. The lower end of this strut 2 is curved forwardly and has attachedatits extreme lower end the swinging lever arm. 3 as by means of the pivot The ski 5 is provided with pedestal 6 which is pivoted at the rearward end of the lever arm 3- as by means of the pivot pin 1.

Shock absorbing means of the usual type is interposed between the strut 2 and the swinging arm: 3, this shock absorbing means, as-illustrated, taking the form of the cylinder 8 disposed adjacent the lower end of strut 2 andin which the piston 9 is adapted to reciprocate. As the piston 9 moves upwardly, it compresses the spring H) which normally tends to urge the piston 9 downwardly. The piston 9 has the port II which is adapted to allow the air from one side of the cylinder 8 to pass through the piston 9' to the other side of the cylinder. Interposed between the piston 9 and the swinging arm 3' is the shock absorber link l2 which is pivoted at'its upper end to the piston 9' and at its lower end to the arm 3 and is adapted to oscillate in the recess i=3 provided therefor in the arm' 3.

Coming now to the locking. device itself; this comprises the stops l4 integrally formed on the ears. 15 of the pedestal 6. These-stops l4 extend inwardly from the inner faces of the ears l5. The stops [4 are adapted to abut against a stop Hiwhichis provided integrally on the upper face of theswinging arm 3. The location of stops l4 and L6 is such that when the lever arm 3 rotates onthe pivot pin 1 in a clockwise direction of the drawings, the stop. I6 is adapted to engage the stops [4 and to prevent further relative movement in that direction betweenthe ski 5 and the swinging arm 3.

Pivotal movement of the ski 5 in the other direction is limited or prevented by the stop H which is formed integrally on one side of the pedestal 6. This stop I! is adapted to be en-' gaged by a stop l8 integrally formed on a rotating dog 19 which is rotatably mounted on the main pin 1. The stop IB' is adapted toengage the stop I! when rotated. in a direction counterclockwise of the. drawings. The dog I9 is provided with an upstanding ear 29 which is disposed on the opposite side of pivot pin 1 from the stop I8. The strut 2 is provided with the integral ear 2!, and the ears 20 and 2| are pivotally interconnected by the parallel link 22 which is pivotally attached at one end to'the strut ear 2!. and at the other end to the dog ear 20.

From the foregoing, it will be seen that the lock formed between the ears l4 and I6 limits the travel of the nose of the ski downwardly, while the lock provided by the stops l1 and [8 if limits the upward travel of the nose of the skipin 4, The30 nose-down freedom of the ski which is I required by C. A. F. Specification M.2/38

is attained after 30 rotation of the swinging lever arm 3, i. e., at about half travel of the strut 2 downward with normal installations. Freedom of pivotal movementof the ski 5 in a direction tending to bring its nose up is afiorded by the action of the rod 22 which moves the dog I9 clockwise as the weight ofthe airplane is rested on the ski., This causes the stop I8 to swing in a clockwise direction away from stop l'l. Thus,

when the airplane is on the ground, there is considerable clearance between stops l1 and I8 but when take-ofi occurs, the expansion of the shock absorber spring I causes the swinging arm 3 to move downwardly towards the ski until the stop l6 has engaged thestops I4. At the same time, the stop l8 engages the stop l1 and this locking action cooperates to prevent rotation of the ski in a clockwise direction.

While the operation will be obvious from the foregoing, it maybe described briefly as follows:

With the airplane on the ground with the tail down, the parts will assume the position shownin Fig. 6, there being sufficient clearance between the stops l6 and M to allow about 15 nose-down travel of the ski, and there bein sufficient clearance between the stops I8 and I I to allow about 30 nose-up travel of the ski. As the tail of theairplane is elevated preparatory to taking on, the parts assume the position of Fig. 4, theslight increase in weight having telescoped still further the spring l0, and the rotation of the swinging arm 3 relative to the ski 5 having caused the distance between stops l6 and M to have increased and the distance between the stops l1 and I8 to decrease. As the airplane takes oif, the load on the ski is progressively reduced and this causes the swinging arm 3 to rise relativeto the ski. This causes a partial constraint of the ski 5 by bringing the pairs of stops closer to one another. This action continues until the moment of take-oil, at which all of the weight of the airplaneis removed from the ski andlthe ski is locked against rotation in either direction, the parts having assumed the position of Fig. 2. On landing, the reverse action takes place. At the moment when the airplane engages the ground, the downward travel of swinging arm 3 causes immediate separation of the stops so that the ski is free to pivot as necessary during the landing. If a made, the ski has ample freedom in either direction,'as is illustrated in Fig. 6. If a tail-up landing is made, the likewise has ample freedom in either direction, as is illustrated in Fig. 4. If

an obstruction tending to move the nose of the ski upwardly is encountered during taxiing or during a three point landing, the parts will assume the position shown inFig. 7 in, which although the ski is tilted upwardly at an angle of about 10, there is still-a freedom of about 20 nose-up travel and about nose-down travel.

Modification of Figures 8 and 9 In the modified form shown in Figs. 8 and 9, the construction'is generally similar to that of the embodiment of Figs. 1 to 7, except that both up and down locks are brought into action by the constraint of rods, whereas in Figs. 1 to 7 only the stops I1 and i8 are controlled by the constraining rod or link 22. In the modified form, a second dog 23 is pivotally mounted on the pin 1 on the other end thereof. This dog 23 has an ear 24 which is linked by a link 25 to anear 26 integrally iormed on the strut 2 below the ear 2|.

three point landing is On the side of the dog 23 opposite the ear 24, a stop 21 is formed and this stop 21 is adapted to abut a stop 28 formed on the pedestal 6. Thus as the swinging arm 3 moves downwardly, it causes by means of the link 22 the stops I1 and [8 to separate in the same manner as that described above, and simultaneously through the link 25 causes the dOg 23 to rotate in a counterclockwise direction, thereby moving the stop 21 forwardly away from the stop 28 rigidly carried by the ski 5. The provision of the crossed link 25 and of the parallel link 22, these links engaging the dogs 7 l9 and 23 on the ends thereof opposite the stops l8 and 27 brings about this result. Upon taking ofi, the upward swinging of the arm 3 and the.

With the form of the invention shown in the modification, the rods 22 and 25 can be so pivoted and proportioned that they limit the freedom of rotation of the ski when on the ground to any predetermined figure. Alternatively, they can be arranged to give very rapid separation of the stop faces during the first part of travel, i. e., 30 of freedom in either direction after 15 rotation of the arm 3, or at one-fourth of the travel, and a separate rotation limiting device or devices can be provided corresponding to the stops l4 and I6 shown in Figs. 1 to 7.

From the foregoing description, it will be seen that the present invention makes possible in a simple and economical manner the positive looking of the ski during flight, the automatic unlocking of the ski for complete freedom of rotation within certain limits upon landing, and the automatic locking of the ski upon take-01f. These advantages are attained without unduly increasing the weight of the landing gear and in amanner which makes for low'maintenance costs.

' I wish it to be understood that I intend to include as within the invention such modifications andadaptations as fall within the terms or the spirit of the appended claims.

Having thus fully described my invention, What I claim as new and desire to secure by Letters Patent is:

1. In an airplane landing gear, a strut carried by the airplane, a swinging lever pivotally mounted on said strut and normally assuming an angle thereto, a ski pivotally mounted on said lever, a member pivotally mounted on said lever about the pivotal axis of said ski, a stop rigidly carried on said member, a stop rigidly carried on said ski and adapted to abut against said stop on said member, and means for rotating said memher to separate its stop from said ski stop when the airplane is on the ground and to cause said stops to engage one another when the air lane is in the air.

2. In an airplane landing gear, a strut carried by the airplane, a swinging lever pivotally mounted on said strut and normally assuming an angle relative thereto, a ski pivotally mounted on said lever, a member pivotally mounted on said lever about the pivotal axis of said ski, a stop rigidly carried on said member, a stop rigidly carried on said ski andadapted to abut against said stop on said member, and means interconnecting said member and said strut and pivotally connected to said member and said strut for rotating said member to separate its stop from said ski strut when the airplane is on the ground and to cause said stops to engage one another when the airplane is in the air.

3. In an airplane landing gear, a strut carried by the airplane, a swinging lever pivotally carried on said strut, a ski pivotally carried on said lever, a stop rigidly carried on said ski, a rotating dog pivotally mounted on the pivotal axis of said ski, a locking stop rigidly carried by said dog and adapted to engage said ski stop, and a lever disposed generally parallel to said swinging lever and pivotally connected to said strut and to said dog for rotating said dog to disengage said locking stop from said ski stop and allow free pivoting of said ski when the airplane is on the ground and to engage said locking stop with said ski stop and prevent pivoting of said ski when the airplane is in the air.

4. In an airplane landing gear, a landing gear strut, a swinging lever pivoted thereto, a ski pivoted to said lever, a pair of oppositely acting stops rigidly carried on said ski, a locking stop rigidly carried on said lever and adapted to engage one of said ski stops to limit rotation of said ski in one direction, a dog pivoted on the same axis as said ski, a locking stop rigidly carried on said dog and adapted to engage the other of said ski stops to limit rotation of said ski in the other direction, and an operating member pivoted to said strut and to said dog for rotating said dog so as to disengage its locking stop from the ski stop associated therewith and allow limited rotation of said ski when the airplane is on the ground and to engage said locking stop on said dog with said ski stop and prevent rotation of said ski when the airplane is in the air.

5. In an airplane landing gear, a landing gear strut, a swinging lever pivoted thereto, a ski pivoted to said lever, a pair of oppositely acting stops rigidly carried on said ski, a locking stop rigidly carried on said lever and adapted to engage one of said ski stops to limit rotation of said ski in one direction, a dog pivoted on the same axis as said ski, a locking stop rigidly car'- ried on said dog and adapted to engage the other of said ski stops to limit rotation of said ski in the other direction, and an operating member pivoted to said strut and to said dog for rotating said dog so as to disengage its locking stop from the ski stop associated therewith and allow limited rotation of said ski when the airplane is on the ground and to engage said locking stop on said dog with said ski stop and prevent rotation of said ski when the airplane is in the air, said operating member being disposed generally parallel to said swinging lever.

6. In an airplane landing gear, a landing gear strut, a swinging lever pivoted thereto, a ski pivoted to said lever, a pair of oppositely acting stops rigidly carried on said ski, a locking stop rigidly carried on said lever and adapted to engage one of said ski stops to limit rotation of said ski in one direction, a dog pivoted on the same axis as said ski, a locking stop rigidly carried on said dog and adapted to engage the other of said ski stops to limit rotation of said ski in the other direction, and an operating member pivoted to said strut and to said dog for rotating said dog so as to disengage its locking stop from the ski stop associated therewith and allow limited rotation of said ski when the airplane is on the ground and to engage said locking stop on said dog with said ski stop and prevent rotation of said ski when the airplane is in the air, said operating member being disposed generally parallel to said swinging lever and pivotally connected to said dog on the other side of said dog from said locking stop.

'7. In an airplane landing gear, a landing strut, a swinging arm pivotally mounted on said strut, a ski pivotally mounted on said arm, a pair of oppositely directed stops rigidly carried on said ski, a locking stop on said swinging arm adapted to engage one of said ski stops and thereby prevent pivoted movement of said ski in one direction as said arm swings away from said ski and to move away from said one of said ski stops and thereby permit limited movement of said ski in said direction as said arm swings towards said ski, the amount of said limited movement increasing with the amount of swing of said arm towards said ski, a locking stop adapted to engage the other of said ski stops and thereby prevent pivotal movement of said ski in the other direction, and means interconnecting said lastnamed locking stop and said strut for causing said last-named locking stop to move away from said other ski stop an amount increasing with the amount of movement of said strut towards said ski.

3. In an airplane landing gear, a landing strut,

a swinging arm pivotally mounted on said strut, a ski pivotally mounted on said arm, a pair of oppositely directed stops rigidly carried by said ski, a pair of oppositely directed movable locking stops adapted to cooperatively engage said ski stops and prevent pivotal movement of said ski in either direction, and means interconnecting each of said locking stops with said strut in such manner that each of said locking stops is moved away from its corresponding ski stop an amount which increases with the movement of said strut towards said ski, said locking stops moving in opposite senses of direction.

9. In an airplane landing gear, a landing strut, a swinging arm pivotally carried thereby, shock absorber means between said strut and said arm and urging said arm downwardly, a ski pivotally carried on said arm, a pair of oppositely directed stops fixedly carried by said ski, a pair of rotatable dogs pivotally mounted on the pivotal axis between said arm and said ski, a locking stop rigidly carried by each of said dogs, said locking stops being oppositely directed and each being adapted to abut one of said ski stops, link means disposed generally parallel to said arm and pivotally interconnecting one of said dogs and said strut and adapted to push the locking stop on the dog which it engages away from its cooperating ski stop as said strut moves towards said ski, and crossed link means crossing said arm and pivotally interconnecting the other of said dogs and said strut and adapted to push the locking stop on the dog which it engages away from its cooperating ski stop as said strut moves towards said ski.

WILLIAM ARMSTRONG. 

